Merge tag 'bitmap-for-6.10v2' of https://github.com/norov/linux

Pull bitmap updates from Yury Norov:

 - topology_span_sane() optimization from Kyle Meyer

 - fns() rework from Kuan-Wei Chiu (used in cpumask_local_spread() and
   other places)

 - headers cleanup from Andy

 - add a MAINTAINERS record for bitops API

* tag 'bitmap-for-6.10v2' of https://github.com/norov/linux:
  usercopy: Don't use "proxy" headers
  bitops: Move aligned_byte_mask() to wordpart.h
  MAINTAINERS: add BITOPS API record
  bitmap: relax find_nth_bit() limitation on return value
  lib: make test_bitops compilable into the kernel image
  bitops: Optimize fns() for improved performance
  lib/test_bitops: Add benchmark test for fns()
  Compiler Attributes: Add __always_used macro
  sched/topology: Optimize topology_span_sane()
  cpumask: Add for_each_cpu_from()

Author: torvalds

MAINTAINERS

@@ -3725,6 +3725,20 @@ F:	tools/include/vdso/bits.h
 F:	tools/lib/bitmap.c
 F:	tools/lib/find_bit.c
 
+BITOPS API
+M:	Yury Norov <[email protected]>
+R:	Rasmus Villemoes <[email protected]>
+S:	Maintained
+F:	arch/*/include/asm/bitops.h
+F:	arch/*/include/asm/bitops_32.h
+F:	arch/*/include/asm/bitops_64.h
+F:	arch/*/lib/bitops.c
+F:	include/asm-generic/bitops
+F:	include/asm-generic/bitops.h
+F:	include/linux/bitops.h
+F:	lib/test_bitops.c
+F:	tools/*/bitops*
+
 BLINKM RGB LED DRIVER
 M:	Jan-Simon Moeller <[email protected]>
 S:	Maintained

include/linux/bitops.h

@@ -8,13 +8,6 @@
 
 #include <uapi/linux/kernel.h>
 
-/* Set bits in the first 'n' bytes when loaded from memory */
-#ifdef __LITTLE_ENDIAN
-#  define aligned_byte_mask(n) ((1UL << 8*(n))-1)
-#else
-#  define aligned_byte_mask(n) (~0xffUL << (BITS_PER_LONG - 8 - 8*(n)))
-#endif
-
 #define BITS_PER_TYPE(type)	(sizeof(type) * BITS_PER_BYTE)
 #define BITS_TO_LONGS(nr)	__KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(long))
 #define BITS_TO_U64(nr)		__KERNEL_DIV_ROUND_UP(nr, BITS_PER_TYPE(u64))
@@ -257,16 +250,10 @@ static inline unsigned int __ffs64(u64 word)
  */
 static inline unsigned int fns(unsigned long word, unsigned int n)
 {
-	unsigned int bit;
-
-	while (word) {
-		bit = __ffs(word);
-		if (n-- == 0)
-			return bit;
-		__clear_bit(bit, &word);
-	}
+	while (word && n--)
+		word &= word - 1;
 
-	return BITS_PER_LONG;
+	return word ? __ffs(word) : BITS_PER_LONG;
 }
 
 /**

include/linux/compiler_attributes.h

@@ -361,6 +361,19 @@
  */
 #define __used                          __attribute__((__used__))
 
+/*
+ * The __used attribute guarantees that the attributed variable will be
+ * always emitted by a compiler. It doesn't prevent the compiler from
+ * throwing 'unused' warnings when it can't detect how the variable is
+ * actually used. It's a compiler implementation details either emit
+ * the warning in that case or not.
+ *
+ * The combination of both 'used' and 'unused' attributes ensures that
+ * the variable would be emitted, and will not trigger 'unused' warnings.
+ * The attribute is applicable for functions, static and global variables.
+ */
+#define __always_used			__used __maybe_unused
+
 /*
  *   gcc: https://gcc.gnu.org/onlinedocs/gcc/Common-Function-Attributes.html#index-warn_005funused_005fresult-function-attribute
  * clang: https://clang.llvm.org/docs/AttributeReference.html#nodiscard-warn-unused-result

include/linux/cpumask.h

@@ -385,6 +385,16 @@ unsigned int __pure cpumask_next_wrap(int n, const struct cpumask *mask, int sta
 #define for_each_cpu_or(cpu, mask1, mask2)				\
 	for_each_or_bit(cpu, cpumask_bits(mask1), cpumask_bits(mask2), small_cpumask_bits)
 
+/**
+ * for_each_cpu_from - iterate over CPUs present in @mask, from @cpu to the end of @mask.
+ * @cpu: the (optionally unsigned) integer iterator
+ * @mask: the cpumask pointer
+ *
+ * After the loop, cpu is >= nr_cpu_ids.
+ */
+#define for_each_cpu_from(cpu, mask)				\
+	for_each_set_bit_from(cpu, cpumask_bits(mask), small_cpumask_bits)
+
 /**
  * cpumask_any_but - return a "random" in a cpumask, but not this one.
  * @mask: the cpumask to search

include/linux/find.h

@@ -222,7 +222,7 @@ unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
  *	 idx = find_first_bit(addr, size);
  *
  * Returns the bit number of the N'th set bit.
- * If no such, returns @size.
+ * If no such, returns >= @size.
  */
 static inline
 unsigned long find_nth_bit(const unsigned long *addr, unsigned long size, unsigned long n)

include/linux/wordpart.h

@@ -39,4 +39,11 @@
  */
 #define REPEAT_BYTE(x)	((~0ul / 0xff) * (x))
 
+/* Set bits in the first 'n' bytes when loaded from memory */
+#ifdef __LITTLE_ENDIAN
+#  define aligned_byte_mask(n) ((1UL << 8*(n))-1)
+#else
+#  define aligned_byte_mask(n) (~0xffUL << (BITS_PER_LONG - 8 - 8*(n)))
+#endif
+
 #endif // _LINUX_WORDPART_H

kernel/sched/topology.c

@@ -2353,7 +2353,7 @@ static struct sched_domain *build_sched_domain(struct sched_domain_topology_leve
 static bool topology_span_sane(struct sched_domain_topology_level *tl,
 			      const struct cpumask *cpu_map, int cpu)
 {
-	int i;
+	int i = cpu + 1;
 
 	/* NUMA levels are allowed to overlap */
 	if (tl->flags & SDTL_OVERLAP)
@@ -2365,9 +2365,7 @@ static bool topology_span_sane(struct sched_domain_topology_level *tl,
 	 * breaking the sched_group lists - i.e. a later get_group() pass
 	 * breaks the linking done for an earlier span.
 	 */
-	for_each_cpu(i, cpu_map) {
-		if (i == cpu)
-			continue;
+	for_each_cpu_from(i, cpu_map) {
 		/*
 		 * We should 'and' all those masks with 'cpu_map' to exactly
 		 * match the topology we're about to build, but that can only

lib/Kconfig.debug

@@ -2482,7 +2482,6 @@ config TEST_LKM
 
 config TEST_BITOPS
 	tristate "Test module for compilation of bitops operations"
-	depends on m
 	help
 	  This builds the "test_bitops" module that is much like the
 	  TEST_LKM module except that it does a basic exercise of the

lib/find_bit.c

@@ -87,7 +87,7 @@ out:										\
 	if (sz % BITS_PER_LONG)							\
 		tmp = (FETCH) & BITMAP_LAST_WORD_MASK(sz);			\
 found:										\
-	sz = min(idx * BITS_PER_LONG + fns(tmp, nr), sz);			\
+	sz = idx * BITS_PER_LONG + fns(tmp, nr);				\
 out:										\
 	sz;									\
 })

lib/test_bitmap.c

@@ -244,7 +244,7 @@ static void __init test_find_nth_bit(void)
 	expect_eq_uint(60,  find_nth_bit(bmap, 64 * 3, 5));
 	expect_eq_uint(80,  find_nth_bit(bmap, 64 * 3, 6));
 	expect_eq_uint(123, find_nth_bit(bmap, 64 * 3, 7));
-	expect_eq_uint(64 * 3, find_nth_bit(bmap, 64 * 3, 8));
+	expect_eq_uint(0,   !!(find_nth_bit(bmap, 64 * 3, 8) < 64 * 3));
 
 	expect_eq_uint(10,  find_nth_bit(bmap, 64 * 3 - 1, 0));
 	expect_eq_uint(20,  find_nth_bit(bmap, 64 * 3 - 1, 1));
@@ -254,7 +254,7 @@ static void __init test_find_nth_bit(void)
 	expect_eq_uint(60,  find_nth_bit(bmap, 64 * 3 - 1, 5));
 	expect_eq_uint(80,  find_nth_bit(bmap, 64 * 3 - 1, 6));
 	expect_eq_uint(123, find_nth_bit(bmap, 64 * 3 - 1, 7));
-	expect_eq_uint(64 * 3 - 1, find_nth_bit(bmap, 64 * 3 - 1, 8));
+	expect_eq_uint(0,   !!(find_nth_bit(bmap, 64 * 3 - 1, 8) < 64 * 3 - 1));
 
 	for_each_set_bit(bit, exp1, EXP1_IN_BITS) {
 		b = find_nth_bit(exp1, EXP1_IN_BITS, cnt++);